I agree with most of what you're saying. This discussion is veering off a bit into the whole "functional" thing.
No exercise is inherently bad or useless. Do I think there are many more exercises that are less contrived, more "natural/functional", and in all likelihood more transferable to athletic activities than the GHR (or GHD sit-up for that matter)? Yes. Could it be towards the bottom of the toolbox, assuming I have several hundred dollars to spend on a gigantic piece of equipment that sits far down on the hierarchy? Sure.
Like expensive tools that only have a minimal range of uses, I'd likely go use someone else's on the rare occasion I needed it. I have a 70's era hyperextension / Roman Chair set-up that I bought on Craigslist for $50 that takes up half the space of a GHD that works just fine for what I need it to. Cheaper, pretty versatile, and much smaller footprint.
Many people's toolboxes are too small (see garage gyms), their tool budget isn't that big (heck, a whole set of bumpers and maybe a cheap bar can be had for the price of a good GHD), or their training time constraints don't allow them to utilize many of the tools that sit way at the bottom of the toolbox.
My priorities in exercise selection sit with these starting points:
- Feet and/or body are on solid ground (terrestrial-based)
- Hanging from something (arboreal-based)
- Supporting myself with my arms (could be either)
PL, OL, and gymnastics/calisthenic-based movements typically fit in one of those major categories. Contraptions that hold the body in place (especially by holding the feet), elevated above the ground, do not--hence they fall way to the bottom of my toolbox.